Chemistry Reference
In-Depth Information
dinotefuran under the low rainfall regimen only through early June, as compared with
plants that received no insecticide; CPB mortality on plants treated with dinotefuran under
the high rainfall regimen were not significantly different than the untreated on all dates
observed. A highly water-soluble systemic insecticide may not provide long-term control or
regulation compared with a less water-soluble systemic insecticide [28]. Mortality of CPB
gradually on foliage treated with imidacloprid or thiamethoxam declined over time from
May through July for both rainfall regimens, and mortality declined more quickly with
dinotefuran for the low rainfall regimen as compared with imidacloprid or thiamethoxam.
Data from the field trials for CPB mortality are similar to the CPB mortality trials in the
laboratory bioassay, with significant insecticide effects in that plots treated with either
Admire or Platinum at planting resulting in significantly fewer CPB/3 hills through late June
under both the low and high rainfall regimens. Plots treated with dinotefuran had
significantly fewer CPB/3 hills than did plots that received no insecticide only on 2 Jun and
only under the low rainfall regimen; there were no significant differences for CPB/3 hills
between plots treated with dinotefuran and the no-insecticide plots on all dates observed
under the high rainfall regimen. As was recorded with the CPB larval counts in the field and
the laboratory trials, dinotefuran was less effective than either imidacloprid or
thiamethoxam under the low rainfall regimen, and dinotefuran was ineffective under the
high rainfall regimen. Further, both imidacloprid and thiamethoxam remained effective for
a greater time period after planting than did dinotefuran, possibly due to the lower
solubility of imidacloprid and thiamethoxam. Field data for the percentage defoliation
caused by CPB feeding were similar to that observed for CPB mortality. Significant
insecticide effects were observed as defoliation increased over time. Defoliation in plots
treated with either imidacloprid or thiamethoxam remained low through all observation
dates, but defoliation in plots treated with dinotefuran was not significantly different than
plots that received no insecticide on any observation date. These data agree with [29], who
reported that potatoes treated with dinotefuran had significantly greater percentage
defoliation than either imidacloprid or thiamethoxam in white potatoes with in-furrow
treatments.
The PLH data show significant insecticide and significant rainfall effects. Under the low
rainfall regimen, all insecticides resulted in significantly less PLH damage through the
season (mid- June through mid-July) as compared with the plots that received no
insecticide; no significant effects among the three insecticides were observed for either
observation date. However, under the high rainfall regimen, plots treated with either
imidacloprid or thiamethoxam resulted in significantly less (P<0.05) PLH damage early in
the season (25 Jun) than did all other treatments, but only plots treated with thiamethoxam
had significantly (P<0.05) less PLH damage than all other treatments on 7 July. Our data
agrees with that of [30], who reported that thiamethoxam provided longer and more
consistent protection of snap beans from PLH than did imidacloprid when applied as a seed
treatment. They concluded that thiamethoxam had greater physiological activity against
PLH than did imidacloprid.
